Effect of Plate Manipulators on Coherent Structures in a Turbulent Boundary Layer

摘要

An experimental investigation was carried out to examine the effects ofmanipulator blades on the Reynolds-stress production process in the log layer of a turbulent boundary layer. A three-dimensional sampling grid was used to investigate the effect of manipulators on the ensemble-averaged velocities and pseudoinstantaneous distributions of the structures associated with Reynolds-stress producing events detected at the wall over the Reynolds number range 3400 < Re. < 5200. The effect of manipulators on the ejection frequency for 3000 < Re. < 10,000 was found to be small. Furthermore, a reduction of the three-dimensional structure was observed only for the larger scales associated with the production process, and a return to conditions equivalent to a regular boundary layer was documented over approximately 100 boundary-layer thicknesses downstream of the manipulators. The results suggest that the larger (outer) structures of boundary layers play only a partial role in the wall process and that this production process can be incipiently generated and self sustained.